Formation, dissociation, and diffusion of various hydrogen dimers in silicon

Available data on hydrogen in silicon samples quenched from a high T and in those exposed to a plasma at low T are analyzed and the existence of three different forms of diatomic hydrogen is concluded. One of them, H2A (a dimer of a moderate diffusivity) was fully characterized by the temperature dependence of its dissociation rate constant and its equilibrium constant and diffusivity. The two other forms, H2B (of a high diffusivity) and H2C (of a low diffusivity) are partially characterized. As a practical application of the properties of the dimers deduced here, the hydrogen content in solar cells was estimated from data on the permanent deactivation of boron–oxygen centers that degrade solar cell efficiency.